Ultrasonic-intensified chemical cleaning of a nano filtration membrane in an oilfield sewage purification system was studied in detail. The most extreme conditions of chemical dissolving of scalants evaluated in this study were dissolving agent SSA-I concentration of 60 g/L, temperature of 75oC, and reaction time of 6 h respectively. With a lower solution concentration of SSA-I (45 g/L), a temperature of 50oC, and a time of 4 h, ultrasonic-intensified chemical cleaning of nano filtration membrane achieved higher efficiency. Specifically, the measured percentage of scalant dissolved rose from 91.0% to 99.1%, the speed of scale- dissolving rose from 1.896 g/(L·h) to 2.478 g/(L·h) and the amount of scalant dissolved rose from 0.152 g/g to 0.220 g/g in comparison to pure chemical dissolving. The industrial application results also indicated that the membrane-flux recovery rate had been improved to 95.6% by the way of ultrasonic-intensified chemical cleaning, much higher than the original 49.1% of high-strength chemical cleaning. Hence, ultrasound effectively strengthens the chemical cleaning effect of nano filtration membranes.
Present State and Prospective of Reverse Osmosis and Nano–Filtration Membranes
